public double CalculateTotalExpense(Category category)
 {
     double TotalExpense = 0;
     foreach (var userbalance in UserBalances)
     {
         if (userbalance.ExpensesPerCategory.ContainsKey(category))
         {
             TotalExpense += userbalance.ExpensesPerCategory[category];
         }
     }
     return TotalExpense;
 }
 public void Save(Category entity)
 {
     this.session.Store(entity);
 }
 public void Remove(Category entity)
 {
     throw new NotImplementedException();
 }
 public double CalculateTotalExpensePerDay(Category category)
 {
     double TotalExpense = CalculateTotalExpense(category);
     int TotalDays = UserBalances.Sum(ub => ub.DaysPresent);
     return TotalExpense/TotalDays;
 }